A drug reaction resulting from immune complex deposition is classified as which type of hypersensitivity reaction?

A drug reaction that results from immune complex deposition is classified as a Type III hypersensitivity reaction. In this type of hypersensitivity, the immune system produces antibodies in response to an antigen, and these antibodies form immune complexes that can deposit in various tissues. This deposition can lead to inflammation and tissue damage as the immune system becomes activated and recruits inflammatory cells to the site of the immune complexes.

In the context of drug reactions, certain medications can trigger the formation of these immune complexes, leading to conditions such as serum sickness or other drug-related hypersensitivity reactions characterized by symptoms like fever, rash, and arthralgia. The key element in Type III reactions is the involvement of circulating immune complexes rather than direct cell damage or inflammation caused by sensitized T-cells, as seen in other types of hypersensitivity reactions.

Type I reactions, often associated with allergic responses, involve immediate hypersensitivity mediated by IgE antibodies. Type II reactions primarily involve the destruction of target cells through IgG or IgM antibodies and complement activation, typically directed at antigens on cell surfaces. Type IV reactions are delayed-type and mediated by T-lymphocytes, where no antibodies are involved. Thus, in the case of drug reactions linked to immune complex deposition, recognizing it